This invention relates generally to forming of fiber composites, for example as are used in air filtration; and more particularly, the invention concerns provision of a filter composite comprising multiple layers of porous materials, of such characteristics as enable the composite to be self-supporting, i.e., without need for wire backing or other auxiliary support adjacent areal extents of the composite. Such wireless composites are of great advantage, as respects ease of manufacture, use in filtering, and ease of disposal. Wire-supported filters require wire trimming, producing sharp edges which can and do injure hands of workers manufacturing filters.
There is need for longer-life filters capable of efficiently filtering particulate from gas streams, and there is need for efficient, effective methods of producing such filters. There is also need for preventing escape of smaller diameter fibers from filter structures.
The disclosures of U.S. Pat. Nos. 3,690,852 and 5,985,411 are incorporated herein, by reference.
It is a major object of the invention to provide an improvement filter composites meeting the above needs. That composite basically comprises
a) a first layer of glass fibers having random orientation, and
b) synthetic resinous fibers extending in close association with the glass fibers.
As will be seen, the synthetic resinous fibers may be distributed in mixed relation with the glass fibers of the first layer; or the synthetic resinous fibers may extend in a layer separate from but adjacent to the first layer glass fibers. Both such modes of synthetic fiber disposition may be employed in a filter composite employing glass fibers. Typically, the synthetic resinous fibers may comprise between 10% and 60% by volume of the total composite volume of both glass and synthetic resin fibers. The synthetic resinous fibers may typically consist of polyester resin.
Another object is to provide an additional porous layer which blocks escape of fibers, to consist essentially of non-woven, synthetic fiber, examples being CEREX, non-woven NYLON or RAYON. The latter is provided as an air-laid, NYLON, or RAYON non-woven layer. That additional layer is typically bonded to the glass fiber layer during the manufacturing process.
A further object includes provision of bonding resin adherent to the fibers in such layers, the filter composite being porous. The to bonding resin typically is applied to saturate the described layer or layers, excess resin being removed, as by vacuum application to the composite, whereby porosity of the composite is maintained or provided.
Yet another object is to provide a composite having synthetic resinous fibers with crimped or hollow shapes, and straight shafts, and wherein the bulk of the glass fibers have:
i) diameters between 1 and 16 microns
ii) lengths between xc2xc and 1xc2xd inches.
The filter composite typically has weight between 0.01 and 0.05 lbs, per square foot; and thickness between 0.02 and 0.10 inches.
A yet further object includes:
a) providing a first layer of glass fibers having random orientation,
b) providing an additional layer of non-woven NYLON or RAYON fibers extending adjacent that first layer,
c) and providing and adhering bonding resin to fibers in such layers, and then removing sufficient of the bonding resin to establish filter porosity, for allowing gas flow through the filter.
As will be seen, the bonding resin consists essentially of thermoplastic resin adapted to be heated during reforming of the filter to selected shape. The filter typically assumes selected shape after heating, reforming, and cooling of the resin; and one advantageous shape comprises folds or pleats, as may be chosen by the user following filter material manufacture and sale.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: